Reducing memory bandwidth consumption when executing a program that uses integral images

ABSTRACT

Methods and apparatuses to reduce memory bandwidth consumption when executing a program that uses integral images are provided. A first integral image representation of a grayscale image may be computed using a first number of bits per pixel. A second integral image representation of the grayscale image may be computed using a second number of bits per pixel. Additionally, an image processing algorithm may be executed on the grayscale image, wherein the size of a rectangle to be used by the image processing algorithm can be determined. Based on the size of the rectangle to be used by the image processing algorithm, it may be determined whether to use the first integral image representation or second integral image representation for the image processing algorithm.

BACKGROUND

An integral image representation of a grayscale image can be used inplace of the grayscale image to efficiently perform image processing onthe grayscale image. Although processing the integral image of agrayscale image can reduce memory bandwidth consumption of imageprocessing algorithms to a certain extent, system constraints may callfor further reduction of memory bandwidth.

BRIEF DESCRIPTION OF THE DRAWINGS

The various advantages of the embodiments of the present invention willbecome apparent to one skilled in the art by reading the followingspecification and appended claims, and by referencing the followingdrawings, in which:

FIG. 1 is a block diagram illustrating an example computer systemoperable to reduce the memory bandwidth consumption when executing aprogram that uses integral images;

FIG. 2A illustrates the integral image representation of a grayscaleimage;

FIG. 2B illustrates how the integral image representation can be used tocalculate the sum of pixel values of the original grayscale image in arectangular area;

FIG. 3 is a flowchart of an example of a method of reducing the memorybandwidth consumption when executing a program that uses integral imagesaccording to an embodiment;

FIG. 4 is a flowchart of an example of a method of reducing the memorybandwidth consumption when executing a program that uses integral imagesaccording to another embodiment;

FIG. 5 is a block diagram illustrating an example system of thisdisclosure; and

FIG. 6 is a block diagram illustrating an example small form factordevice in which components of the system of FIG. 5 may be embodied.

DETAILED DESCRIPTION

Various implementations of this disclosure provide apparatuses andmethods for reducing memory bandwidth consumption when executing aprogram that uses integral images.

FIG. 1 illustrates an example computer system 100 operable to reduce thememory bandwidth consumption when executing a program that uses integralimages. The system 100 can include a processor 105 coupled to a buscontroller 110 via a CPU bus 120. The bus controller 110 can include amemory controller 115. In some implementations, the memory controller115 can be external to the bus controller 110. The memory controller 115can interface the processor 105 to a system memory 125 via a memory bus127. In some implementations, the system memory 125 can be described asa “main memory” of the system 100.

In some implementations, the system memory 125 can store information andinstructions to be executed by processor 105. The system memory 125 maystore data (e.g., integral image data) that is to be accessed by theprocessor to implement, for example, code to execute image and videoprocessing applications that use integral images. The system memory 125may include dynamic random access memory (DRAM) modules that areaccessed by the memory controller 115.

The computer system 100 may also include a read only memory (ROM) 124(and/or other static storage device) coupled to the memory bus 127 tostore static information and instructions for the processor 105. A datastorage device 126 (e.g., a magnetic disk, optical disk, and/or othermachine readable media) may also be coupled to memory bus 127 to storeinformation and instructions for processor 105. For example, the datastorage device 126 can include code to execute image and videoprocessing applications (e.g., computer vision, face detection, orfeature detection modules and/or algorithms) that use integral images.

As shown in FIG. 2A, the integral image representation of a grayscaleimage at pixel (x,y) 200 can be the sum of the pixel values of theoriginal grayscale image above and to the left of pixel (x,y). Thus,referring to FIG. 2B, the integral image representation can be used tocalculate the sum of the pixel values of the original grayscale image ina rectangular area 205 using the integral image values at the corners205 a-d of the rectangle 205. More specifically, the sum of the pixelvalues of the original grayscale image in the rectangle 205 may equalthe integral image representation of the grayscale image at pixel 205 dminus the integral image representation of the grayscale image at pixel205 b minus the integral image representation of the grayscale image atpixel 205 c plus the integral image representation of the grayscaleimage at pixel 205 a.

In existing systems, the number of bits used for each pixel in theintegral image representation of the original grayscale image is basedon the size of the largest rectangle to be used by the image processingalgorithm and the number of bits used for each pixel in the originalgrayscale image. For example, if the number of bits used for each pixelin the original grayscale image is 8-bits and the largest rectangle tobe used by an image processing algorithm is 512×512, the number of bitsused for each pixel in the integral image representation of the originalgrayscale image is at least 26 bits to represent the largest sum of thepixel values of the original grayscale image to be calculated by theimage processing algorithm.

FIG. 3 illustrates a process 300 to reduce the memory bandwidthconsumption when executing a program that uses integral images. At stage305, a first integral image representation of a grayscale image iscomputed and stored using a first number of bits per pixel. In someimplementations, the first number of bits per pixel may be sufficient torepresent the largest sum possible of the pixels in the grayscale imagein a rectangle that is smaller than the largest rectangle to be used bythe image processing algorithm.

Stage 310 may provide for computing and storing a second integral imagerepresentation of a grayscale image using a second number of bits perpixel. In some implementations, the second number of bits per pixel maybe greater than the first number of bits per pixel. In someimplementations, the second number of bits per pixel may be sufficientto represent the largest sum possible of the pixels in the grayscaleimage in the largest rectangle to be used by the image processingalgorithm.

At stage 315, it is determined the size of a rectangle to be used by animage processing algorithm. At stage 320, based on the size of therectangle to be used by the image processing algorithm, either the firstintegral image representation or the second integral imagerepresentation of the grayscale image is used by the image processingalgorithm. Stages 315-320 may be repeated for each rectangle processedby the image processing algorithm. Of particular note is that by usingfewer bits to represent the integral image representation for smallerrectangles processed by the image processing algorithm, the memorybandwidth consumption can be reduced.

FIG. 4 illustrates another process 400 to reduce the memory bandwidthconsumption when executing a program that uses integral images. At stage405, an original integral image representation of a grayscale image iscomputed using a first number of bits per pixel. In someimplementations, the first number of bits per pixel may be sufficient torepresent the largest sum possible of the pixels in the grayscale imagein the largest rectangle to be used by the image processing algorithm.

A first integral image representation of the grayscale image may bestored at block 410 using a number of the least significant bits of theoriginal integral image representation. The number of the leastsignificant bits may be sufficient to represent the largest sum possibleof the pixels in the grayscale image in a rectangle that is smaller thanthe largest rectangle to be used by the image processing algorithm.

At stage 415, a second integral image representation of the grayscaleimage is stored using a number of the most significant bits of the firstintegral image representation. In some implementations, the number ofthe most significant bits of the first integral image are the remainingbits of the first integral image representation that were not used atstage 410.

At stage 420, it is determined the size of a rectangle to be used by animage processing algorithm. Based on the size of the rectangle to beused by the image processing algorithm, either the first integral imagerepresentation or both the first integral image representation and thesecond integral image representation of the grayscale image is used bythe image processing algorithm at illustrated stage 425. Stages 42-425may be repeated for each pixel location processed by the imageprocessing algorithm.

Computing devices contemplated to be within the scope of this disclosureinclude personal computer (PC), laptop computer, ultra-laptop computer,tablet, touch pad, portable computer, handheld computer, palmtopcomputer, personal digital assistant (PDA), cellular telephone,combination cellular telephone/PDA, television, smart device (e.g.,smart phone, smart tablet or smart television), mobile internet device(MID), messaging device, data communication device, and so forth.

FIG. 5 illustrates an example embodiment of a system 500 of thisdisclosure comprising a platform 502, a display 520, content servicesdevice(s) 530, content delivery device(s) 540, and navigation controller550. In embodiments, system 500 may be a media system although system500 is not limited to this context. For example, components of system500 may be incorporated into a personal computer (PC), laptop computer,ultra-laptop computer, tablet, touch pad, portable computer, handheldcomputer, palmtop computer, personal digital assistant (PDA), cellulartelephone, combination cellular telephone/PDA, television, smart device(e.g., smart phone, smart tablet or smart television), mobile internetdevice (MID), messaging device, data communication device, and so forth.

In embodiments, system 500 comprises a platform 502 coupled to a display520. Platform 502 may receive content from a content device such ascontent services device(s) 530 or content delivery device(s) 540 orother similar content sources. A navigation controller 550 comprisingone or more navigation features may be used to interact with, forexample, platform 502 and/or display 520. Each of these components isdescribed in more detail below.

In embodiments, platform 502 may comprise any combination of a chipset505, processor 510, memory 512, storage 514, graphics subsystem 515,applications 516 and/or radio 518. Chipset 505 may provideintercommunication among processor 510, memory 512, storage 514,graphics subsystem 515, applications 516 and/or radio 518. For example,chipset 505 may include a storage adapter (not depicted) capable ofproviding intercommunication with storage 514.

Processor 510 may be implemented as Complex Instruction Set Computer(CISC) or Reduced Instruction Set Computer (RISC) processors, x86instruction set compatible processors, multi-core, or any othermicroprocessor or central processing unit (CPU). In embodiments,processor 510 may comprise dual-core processor(s), dual-core mobileprocessor(s), and so forth.

Memory 512 may be implemented as a volatile memory device such as, butnot limited to, a Random Access Memory (RAM), Dynamic Random AccessMemory (DRAM), or Static RAM (SRAM).

Storage 514 may be implemented as a non-volatile storage device such as,but not limited to, a magnetic disk drive, optical disk drive, tapedrive, an internal storage device, an attached storage device, flashmemory, battery backed-up SDRAM (synchronous DRAM), and/or a networkaccessible storage device. In embodiments, storage 514 may comprisetechnology to increase the storage performance enhanced protection forvaluable digital media when multiple hard drives are included, forexample.

Graphics subsystem 515 may perform processing of images such as stillimages or video for display. Graphics subsystem 515 may be a graphicsprocessing unit (GPU) or a visual processing unit (VPU), for example. Ananalog or digital interface may be used to communicatively couplegraphics subsystem 515 and display 520. For example, the interface maybe any of a High-Definition Multimedia Interface, DisplayPort, wirelessHDMI, and/or wireless HD compliant techniques. In embodiments, graphicssubsystem 515 could be integrated into processor 510 or chipset 505. Inembodiments, graphics subsystem 515 could be a stand-alone cardcommunicatively coupled to chipset 505.

The graphics and/or video processing techniques described herein may beimplemented in various hardware architectures. For example, graphicsand/or video functionality may be integrated within a chipset.Alternatively, a discrete graphics and/or video processor may be used.As still another embodiment, the graphics and/or video functions may beimplemented by a general purpose processor, including a multi-coreprocessor. In a further embodiment, the functions may be implemented ina consumer electronics device.

Radio 518 may include one or more radios capable of transmitting andreceiving signals using various suitable wireless communicationstechniques. Such techniques may involve communications across one ormore wireless networks. Exemplary wireless networks include (but are notlimited to) wireless local area networks (WLANs), wireless personal areanetworks (WPANs), wireless metropolitan area network (WMANs), cellularnetworks, and satellite networks. In communicating across such networks,radio 518 may operate in accordance with one or more applicablestandards in any version.

In embodiments, display 520 may comprise any television type monitor ordisplay. Display 520 may comprise, for example, a computer displayscreen, touch screen display, video monitor, television-like device,and/or a television. Display 520 may be digital and/or analog. Inembodiments, display 520 may be a holographic display. Also, display 520may be a transparent surface that may receive a visual projection. Suchprojections may convey various forms of information, images, and/orobjects. For example, such projections may be a visual overlay for amobile augmented reality (MAR) application. Under the control of one ormore software applications 516, platform 502 may display user interface522 on display 520.

In embodiments, content services device(s) 530 may be hosted by anynational, international and/or independent service and thus accessibleto platform 502 via the Internet, for example. Content servicesdevice(s) 530 may be coupled to platform 502 and/or to display 520.Platform 502 and/or content services device(s) 530 may be coupled to anetwork 560 to communicate (e.g., send and/or receive) media informationto and from network 560. Content delivery device(s) 540 also may becoupled to platform 502 and/or to display 520.

In embodiments, content services device(s) 530 may comprise a cabletelevision box, personal computer, network, telephone, Internet enableddevices or appliance capable of delivering digital information and/orcontent, and any other similar device capable of unidirectionally orbidirectionally communicating content between content providers andplatform 502 and/display 520 directly or via network 560. It will beappreciated that the content may be communicated unidirectionally and/orbidirectionally to and from any one of the components in system 500 anda content provider via network 560. Examples of content may include anymedia information including, for example, video, music, medical andgaming information, and so forth.

Content services device(s) 530 receives content such as cable televisionprogramming including media information, digital information, and/orother content. Examples of content providers may include any cable orsatellite television or radio or Internet content providers. Theprovided examples are not meant to limit embodiments of the invention.

In embodiments, platform 502 may receive control signals from navigationcontroller 550 having one or more navigation features. The navigationfeatures of controller 550 may be used to interact with user interface522, for example. In embodiments, navigation controller 550 may be apointing device that may be a computer hardware component (specificallyhuman interface device) that allows a user to input spatial (e.g.,continuous and multi-dimensional) data into a computer. Many systemssuch as graphical user interfaces (GUI), and televisions and monitorsallow the user to control and provide data to the computer or televisionusing physical gestures.

Movements of the navigation features of controller 550 may be echoed ona display (e.g., display 520) by movements of a pointer, cursor, focusring, or other visual indicators displayed on the display. For example,under the control of software applications 516, the navigation featureslocated on navigation controller 550 may be mapped to virtual navigationfeatures displayed on user interface 522, for example. In embodiments,controller 550 may not be a separate component but integrated intoplatform 502 and/or display 520. Embodiments, however, are not limitedto the elements or in the context shown or described herein.

In embodiments, drivers (not shown) may comprise technology to enableusers to instantly turn on and off platform 502 like a television withthe touch of a button after initial boot-up, when enabled, for example.Program logic may allow platform 502 to stream content to media adaptorsor other content services device(s) 530 or content delivery device(s)540 when the platform is turned “off”. In addition, chip set 505 maycomprise hardware and/or software support for 5.1 surround sound audioand/or high definition 7.1 surround sound audio, for example. Driversmay include a graphics driver for integrated graphics platforms. Inembodiments, the graphics driver may comprise a peripheral componentinterconnect (PCI) Express graphics card.

In various embodiments, any one or more of the components shown insystem 500 may be integrated. For example, platform 502 and contentservices device(s) 530 may be integrated, or platform 502 and contentdelivery device(s) 540 may be integrated, or platform 502, contentservices device(s) 530, and content delivery device(s) 540 may beintegrated, for example. In various embodiments, platform 502 anddisplay 520 may be an integrated unit. Display 520 and content servicedevice(s) 530 may be integrated, or display 520 and content deliverydevice(s) 540 may be integrated, for example. These examples are notmeant to limit the invention.

In various embodiments, system 500 may be implemented as a wirelesssystem, a wired system, or a combination of both. When implemented as awireless system, system 500 may include components and interfacessuitable for communicating over a wireless shared media, such as one ormore antennas, transmitters, receivers, transceivers, amplifiers,filters, control logic, and so forth. An example of wireless sharedmedia may include portions of a wireless spectrum, such as the RFspectrum and so forth. When implemented as a wired system, system 500may include components and interfaces suitable for communicating overwired communications media, such as input/output (I/O) adapters,physical connectors to connect the I/O adapter with a correspondingwired communications medium, a network interface card (NIC), disccontroller, video controller, audio controller, and so forth. Examplesof wired communications media may include a wire, cable, metal leads,printed circuit board (PCB), backplane, switch fabric, semiconductormaterial, twisted-pair wire, co-axial cable, fiber optics, and so forth.

Platform 502 may establish one or more logical or physical channels tocommunicate information. The information may include media informationand control information. Media information may refer to any datarepresenting content meant for a user. Examples of content may include,for example, data from a voice conversation, videoconference, streamingvideo, electronic mail (“email”) message, voice mail message,alphanumeric symbols, graphics, image, video, text and so forth. Datafrom a voice conversation may be, for example, speech information,silence periods, background noise, comfort noise, tones and so forth.Control information may refer to any data representing commands,instructions or control words meant for an automated system. Forexample, control information may be used to route media informationthrough a system, or instruct a node to process the media information ina predetermined manner. The embodiments, however, are not limited to theelements or in the context shown or described in FIG. 5.

As described above, system 500 may be embodied in varying physicalstyles or form factors. FIG. 5 illustrates embodiments of a small formfactor device 500 in which components of system 500 may be embodied. Inembodiments, for example, device 500 may be implemented as a mobilecomputing device having wireless capabilities. A mobile computing devicemay refer to any device having a processing system and a mobile powersource or supply, such as one or more batteries, for example.

As described above, examples of a mobile computing device may include apersonal computer (PC), laptop computer, ultra-laptop computer, tablet,touch pad, portable computer, handheld computer, palmtop computer,personal digital assistant (PDA), cellular telephone, combinationcellular telephone/PDA, television, smart device (e.g., smart phone,smart tablet or smart television), mobile internet device (MID),messaging device, data communication device, and so forth.

Examples of a mobile computing device also may include computers thatare arranged to be worn by a person, such as a wrist computer, fingercomputer, ring computer, eyeglass computer, belt-clip computer, arm-bandcomputer, shoe computers, clothing computers, and other wearablecomputers. In embodiments, for example, a mobile computing device may beimplemented as a smart phone capable of executing computer applications,as well as voice communications and/or data communications. Althoughsome embodiments may be described with a mobile computing deviceimplemented as a smart phone by way of example, it may be appreciatedthat other embodiments may be implemented using other wireless mobilecomputing devices as well. The embodiments are not limited in thiscontext.

As shown in FIG. 6, device 600 may comprise a housing 602, a display604, an input/output (I/O) device 606, and an antenna 608. Device 600also may comprise navigation features 612. Display 604 may comprise anysuitable display unit for displaying information appropriate for amobile computing device. I/O device 606 may comprise any suitable I/Odevice for entering information into a mobile computing device. Examplesfor I/O device 606 may include an alphanumeric keyboard, a numerickeypad, a touch pad, input keys, buttons, switches, rocker switches,microphones, speakers, voice recognition device and software, and soforth. Information also may be entered into device 600 by way ofmicrophone. Such information may be digitized by a voice recognitiondevice. The embodiments are not limited in this context.

Various embodiments may be implemented using hardware elements, softwareelements, or a combination of both. Examples of hardware elements mayinclude processors, microprocessors, circuits, circuit elements (e.g.,transistors, resistors, capacitors, inductors, and so forth), integratedcircuits, application specific integrated circuits (ASIC), programmablelogic devices (PLD), digital signal processors (DSP), field programmablegate array (FPGA), logic gates, registers, semiconductor device, chips,microchips, chip sets, and so forth. Examples of software may includesoftware components, programs, applications, computer programs,application programs, system programs, machine programs, operatingsystem software, middleware, firmware, software modules, routines,subroutines, functions, methods, procedures, software interfaces,application program interfaces (API), instruction sets, computing code,computer code, code segments, computer code segments, words, values,symbols, or any combination thereof. Determining whether an embodimentis implemented using hardware elements and/or software elements may varyin accordance with any number of factors, such as desired computationalrate, power levels, heat tolerances, processing cycle budget, input datarates, output data rates, memory resources, data bus speeds and otherdesign or performance constraints.

One or more aspects of at least one embodiment may be implemented byrepresentative instructions stored on a machine-readable medium whichrepresents various logic within the processor, which when read by amachine causes the machine to fabricate logic to perform the techniquesdescribed herein. Such representations, known as “IP cores” may bestored on a tangible, machine readable medium and supplied to variouscustomers or manufacturing facilities to load into the fabricationmachines that actually make the logic or processor.

Embodiments may therefore include a system including a storage device tostore a program that includes an image processing application, storageto store a first integral image representation of a grayscale imageusing a first number of bits per pixel and a second integral imagerepresentation of the grayscale image using a second number of bits perpixel, and a processor to execute the image processing application usingthe first integral image representation and the second integral imagerepresentation.

Embodiments also may include a method including computing and storing afirst integral image representation of a grayscale image using a firstnumber of bits per pixel, computing and storing a second integral imagerepresentation of the grayscale image using a second number of bits perpixel, executing an image processing algorithm on the grayscale image,determining the size of a rectangle to be used by the image processingalgorithm, and determining whether to use the first integral imagerepresentation or second integral image representation for the imageprocessing algorithm based on the size of the rectangle to be used bythe image processing algorithm.

Embodiments also may include a method including computing an originalintegral image representation of a grayscale image using a first numberof bits per pixel, computing and storing a first integral imagerepresentation of the grayscale image using a number of the leastsignificant bits of the original integral image representation,computing and storing a second integral image representation of thegrayscale image using a number of the most significant bits of theoriginal integral image representation, executing an image processingalgorithm on the grayscale image, determining the size of a rectangle tobe used by the image processing algorithm, and determining whether touse the first integral image representation or both the first integralimage representation and the second integral image representation forthe image processing algorithm based on the size of the rectangle to beused by the image processing algorithm.

Embodiments also may include a computer readable medium including a setof instructions which, if executed by a processor, cause a computer tocompute and store a first integral image representation of a grayscaleimage, compute and store a second integral image representation of thegrayscale, execute an image processing algorithm on the grayscale image,determine a size of a rectangle to be used by the image processingalgorithm, and determine whether to use the first integral imagerepresentation or second integral image representation for the imageprocessing algorithm based on the size of the rectangle to be used bythe image processing algorithm.

Embodiments are applicable for use with all types of semiconductorintegrated circuit (“IC”) chips. Examples of these IC chips include butare not limited to processors, controllers, chipset components,programmable logic arrays (PLAs), memory chips, network chips, and thelike. In addition, in some of the drawings, signal conductor lines arerepresented with lines. Some may be different, to indicate moreconstituent signal paths, have a number label, to indicate a number ofconstituent signal paths, and/or have arrows at one or more ends, toindicate primary information flow direction. This, however, should notbe construed in a limiting manner. Rather, such added detail may be usedin connection with one or more exemplary embodiments to facilitateeasier understanding of a circuit. Any represented signal lines, whetheror not having additional information, may actually comprise one or moresignals that may travel in multiple directions and may be implementedwith any suitable type of signal scheme, e.g., digital or analog linesimplemented with differential pairs, optical fiber lines, and/orsingle-ended lines.

Example sizes/models/values/ranges may have been given, althoughembodiments of the present invention are not limited to the same. Asmanufacturing techniques (e.g., photolithography) mature over time, itis expected that devices of smaller size could be manufactured. Inaddition, well known power/ground connections to IC chips and othercomponents may or may not be shown within the figures, for simplicity ofillustration and discussion, and so as not to obscure certain aspects ofthe embodiments of the invention. Further, arrangements may be shown inblock diagram form in order to avoid obscuring embodiments of theinvention, and also in view of the fact that specifics with respect toimplementation of such block diagram arrangements are highly dependentupon the platform within which the embodiment is to be implemented,i.e., such specifics should be well within purview of one skilled in theart. Where specific details (e.g., circuits) are set forth in order todescribe example embodiments of the invention, it should be apparent toone skilled in the art that embodiments of the invention can bepracticed without, or with variation of, these specific details. Thedescription is thus to be regarded as illustrative instead of limiting.

Some embodiments may be implemented, for example, using a machine ortangible computer-readable medium or article which may store aninstruction or a set of instructions that, if executed by a machine, maycause the machine to perform a method and/or operations in accordancewith the embodiments. Such a machine may include, for example, anysuitable processing platform, computing platform, computing device,processing device, computing system, processing system, computer,processor, or the like, and may be implemented using any suitablecombination of hardware and/or software. The machine-readable medium orarticle may include, for example, any suitable type of memory unit,memory device, memory article, memory medium, storage device, storagearticle, storage medium and/or storage unit, for example, memory,removable or non-removable media, erasable or non-erasable media,writeable or re-writeable media, digital or analog media, hard disk,floppy disk, Compact Disk Read Only Memory (CD-ROM), Compact DiskRecordable (CD-R), Compact Disk Rewriteable (CD-RW), optical disk,magnetic media, magneto-optical media, removable memory cards or disks,various types of Digital Versatile Disk (DVD), a tape, a cassette, orthe like. The instructions may include any suitable type of code, suchas source code, compiled code, interpreted code, executable code, staticcode, dynamic code, encrypted code, and the like, implemented using anysuitable high-level, low-level, object-oriented, visual, compiled and/orinterpreted programming language.

Unless specifically stated otherwise, it may be appreciated that termssuch as “processing,” “computing,” “calculating,” “determining,” or thelike, refer to the action and/or processes of a computer or computingsystem, or similar electronic computing device, that manipulates and/ortransforms data represented as physical quantities (e.g., electronic)within the computing system's registers and/or memories into other datasimilarly represented as physical quantities within the computingsystem's memories, registers or other such information storage,transmission or display devices. The embodiments are not limited in thiscontext.

The term “coupled” may be used herein to refer to any type ofrelationship, direct or indirect, between the components in question,and may apply to electrical, mechanical, fluid, optical,electromagnetic, electromechanical or other connections. In addition,the terms “first”, “second”, etc. may be used herein only to facilitatediscussion, and carry no particular temporal or chronologicalsignificance unless otherwise indicated.

Those skilled in the art will appreciate from the foregoing descriptionthat the broad techniques of the embodiments of the present inventioncan be implemented in a variety of forms. Therefore, while theembodiments of this invention have been described in connection withparticular examples thereof, the true scope of the embodiments of theinvention should not be so limited since other modifications will becomeapparent to the skilled practitioner upon a study of the drawings,specification, and following claims.

We claim:
 1. A method comprising: computing and storing a first integral image representation of a grayscale image using a first number of bits per pixel; computing and storing a second integral image representation of the grayscale image using a second number of bits per pixel; executing an image processing algorithm on the grayscale image; determining the size of a rectangle to be used by the image processing algorithm; and determining whether to use the first integral image representation or second integral image representation for the image processing algorithm based on the size of the rectangle to be used by the image processing algorithm.
 2. The method of claim 1, wherein the first number of bits per pixel are sufficient to represent a largest sum possible of the pixels in the grayscale image in a rectangle that is smaller than a largest rectangle to be used by the image processing algorithm.
 3. The method of claim 1, wherein the second number of bits per pixel is greater than the first number of bits per pixel.
 4. The method of claim 2, wherein the second number of bits per pixel are sufficient to represent the largest sum possible of the pixels in the grayscale image in the largest rectangle to be used by the image processing algorithm.
 5. A system comprising: a storage device to store a program that includes an image processing application; storage to store a first integral image representation of a grayscale image using a first number of bits per pixel and a second integral image representation of the grayscale image using a second number of bits per pixel; and a processor to execute the image processing application using the first integral image representation and the second integral image representation.
 6. The system of claim 5, wherein the first number of bits per pixel are to be sufficient to represent a largest sum possible of pixels in the grayscale image in a rectangle that is smaller than a largest rectangle to be used by the image processing algorithm.
 7. The system of claim 5, wherein the second number of bits per pixel is to be greater than the first number of bits per pixel.
 8. The system of claim 6, wherein the second number of bits per pixel are to be sufficient to represent the largest sum possible of the pixels in the grayscale image in the largest rectangle to be used by the image processing algorithm.
 9. The system of claim 5, wherein the image processing application includes a feature detection module.
 10. The system of claim 5, wherein the image processing application includes a face detection module.
 11. A method comprising: computing an original integral image representation of a grayscale image using a first number of bits per pixel; computing and storing a first integral image representation of the grayscale image using a number of the least significant bits of the original integral image representation; computing and storing a second integral image representation of the grayscale image using a number of the most significant bits of the original integral image representation; executing an image processing algorithm on the grayscale image; determining the size of a rectangle to be used by the image processing algorithm; and determining whether to use the first integral image representation or both the first integral image representation and the second integral image representation for the image processing algorithm based on the size of the rectangle to be used by the image processing algorithm.
 12. The method of claim 11, wherein the first number of bits per pixel are sufficient to represent a largest sum possible of pixels in the grayscale image in a largest rectangle to be used by the image processing algorithm.
 13. The method of claim 11, wherein the number of the least significant bits are sufficient to represent the largest sum possible of the pixels in the grayscale image in a rectangle that is smaller than the largest rectangle to be used by the image processing algorithm.
 14. The method of claim 13, wherein the number of the most significant bits of the original integral image are the remaining bits of the original integral image representation that are not part of the least significant bits.
 15. A computer readable medium comprising a set of instructions which, if executed by a processor, cause a computer to: compute and store a first integral image representation of a grayscale image; compute and store a second integral image representation of the grayscale; execute an image processing algorithm on the grayscale image; determine a size of a rectangle to be used by the image processing algorithm; and determine whether to use the first integral image representation or second integral image representation for the image processing algorithm based on the size of the rectangle to be used by the image processing algorithm.
 16. The computer readable medium of claim 15, wherein the first integral image representation of the grayscale image comprise a first number of bits per pixel.
 17. The computer readable medium of claim 16, wherein the second integral image representation of the grayscale image comprise a second number of bits per pixel.
 18. The computer readable medium of claim 17, wherein the first number of bits per pixel are sufficient to represent a largest sum possible of pixels in the grayscale image in a rectangle that is smaller than a largest rectangle to be used by the image processing algorithm.
 19. The computer readable medium of claim 17, wherein the second number of bits per pixel is greater than the first number of bits per pixel.
 20. The computer readable medium of claim 18, wherein the second number of bits per pixel are sufficient to represent the largest sum possible of the pixels in the grayscale image in the largest rectangle to be used by the image processing algorithm.
 21. The computer readable medium of claim 15, wherein the image processing application is to include a feature detection module.
 22. The computer readable medium of claim 15, wherein the image processing application is to include a face detection module. 